Air heater and circulator



Patented Aug. 8, i950 AIR HEATER AND CIRCULATOR Harry W. Janson, Gray, and Coleman D. Rodgers, Portland, Maine, assignors to Utilities Distributors, Inc., a corporation of Maine Application June 30, 1948, Serial No. 36,116

Claims.

The present invention relates to improvements in space heaters, and more particularly to an improved heater adapted for use in trucks, trailers, freight cars and transportation vehicles generally.

Objects of the invention are to provide an improved space heater unit for use in trucks, trailers, freight cars and the like, which will occupy a minimum of loading space within the vehicle, which will provide for a maximum rate of heating and circulation of air within the vehicle, and which is further constructed and arranged to insure the continuous and efiective cooling of the exterior surfaces of the heater to prevent any possibility of overheating or injury to the load.

The heater unit which forms the subject-matter of the invention, takes the form of a small cylindrical stack which may be in the order of eight to ten inches in diameter, and five feet in height, and is provided in the base portion thereof with a powerful burner unit fired by a propane or similar fuel gas, and a novel arrangement of flues and baffles which has the effect of creating an extremely rapid circulatory draft of air through the heater for the most efficient heating of the carrier space, while at the sametime the external surfaces of the heater are cooled to prevent any possibility of overheating of the portions of the load which may be brought into contact therewith.

A feature of the invention consists in the provision of a Venturi exit cone through which the heated gases from the burner are drawn, and he combination therewith of an entrance bafile cone for introducing said gases through the throat of the Venturi cone at a high velocity, said cones being constructed and arranged to provide for the most efficient channeling of the heated gases through the heater. Further in accordance with the invention, the throat of the Venturi exit cone is arranged with relation to the bafiie entrance cone to permit the drawing of fresh air from the space to be heated which mixes with and has a cooling effect upon the stream of heated gases passing upwardly from the heater. This arrangement has the specific advantage that it greatly increases the rate of circulation of air throughout the space to be heated.

A further feature of the invention consists in the combination of these parts with a cooperating cylindrical outer shell arranged to provide an air inlet space at the lower end thereof and an air outlet at the upper end thereof. The illusstrated heater is so constructed and arranged that the powerful burner provided is most efficiently employed to produce an extremely rapid circulation of moderately heated air without any tendency to discharge excessively hot air from the heater, and Without any tendency to overheating of the external surfaces of the heater unit.

With the above noted and other objects in view as may hereinafter appear, the several features of the invention consist also in the devices, combinations and arrangement of parts hereinafter described and claimed, which together with the advantages to be obtained thereby will be readily understood by one skilled in the art from the following description taken in connection with the accompanying drawing, in which Fig. 1 is a view inside elevation of a space heater illustrating the several features of the invention, with portions broken away to show underlying parts; Fig. 2 is a sectional plan view taken on the line 22 of Fig. 1; and Fig. 3 is a sectional plan View taken on the line 33 of Fig. 1.

The truck trailer heating unit particularly illustrated as embodying in a preferred form the several features of the invention, is of the general type including a gas fired heating unit mounted Within the space to be heated preferabl against the wall of the vehicle and adjacent a door, and a bottle storage unit which may be suspended beneath the body of the vehicle. As specifically shown in the drawings, the heating unit comprises supporting structure in the form of a base plate ill with downwardly extending edge portions l2 providing a raised platform, and vertically extending back plate i similarly formed with flanged edges for engagement with a side wall of the vehicle.

A cylindrical base it open at the bottom and arranged to project beyond the edges of the relatively narrow base plate It provides a housing for a burner unit is including an intake gas line 20, a number of control and safety valves which, forming no part of the invention, will not be specifically described, a thermostat 22 and a vertically disposed burner assembly including a gas pipe 24 and an associated air intake 26 through which air is passed to a mixing chamber 28, and

then passes mixed with gas and air, to the jets of the burner I8. As will be evident from a consideration of Fig. 1, the cylindrical base I5 is provided with a flat ring-shaped cover member 36, which extends inwardly to the edge of the burner l3, and is formed with a cone-shaped flue or baffie 38 through which the heated gases from the burner must pass. With this construction it will be evident that cold air from the floor is drawn upwardly through the open bottom of the cylindrical base It. A portion of the air entering the base chamber is drawn into the burner unit to be mixed in the proper proportion with the gas fuel, and the remainder passes upwardly directly to and around the burner jets into the cone 38. The burner unit above described is of the slotted type as generally indicated in Fig. 3, and is particularly well adapted for use in the truck trailer heater here shown. The burner unit comprises in addition to the central gas fuel supply pipe, the bell-shaped air intake 25 and a mixing chamber generally designated at 28. The construction illustrated has been found to provide a maximum volume of air for admixture with the gas fuel under the most favorable conditions for efiicient combustion.

It will be noted that the thermostat 22 carried in the chamber provided by the cylindrical base 46 is located to be responsive to the incoming cold .air stream from the floor of the vehicle, and

is not influenced by the heat thrown off from or by the warm currents of air rising through the stack above the level of the burner.

The upper or stack portion of the heater comprises a cylindrical shell 46 which is supported above and in axial alignment with the cylindrical base 16 by means of brackets 38 carried on the back plate '54. Directly above the shell '46 there is provided a hot air discharge orifice which takes the form of a cylindrical member :6 ha'ving the same external diameter as the shell 45, and spaced therefrom by means or" supporting straps 52. The upper edge of the cylindrical member 58 is cut on a bias and the top is'covered with a screen to provide a hot air discharge orifice adapted for dischargin hot air in a generally upwardly and outwardly direction away from the wali of the vehicle.

In accordance with the invention, a Venturi cone 54 is provided which is adapted to cooperate with the bafiie cone S3 in controlling the flow of the heated gases from the burner and for effect ing a mixture of cold air therewith in order to effect a very rapid discharge 'of Warm but not superheated air through. the hot air discharge orifice at the upper end of the stack. As best shown in Fig. l, the Venturi cone 5 is arranged in inverted position so that the walls diverge upwardly, thus allowing for expansion and increased rate of flow of the heated air. The upper cone 5 1 at its lower end overlaps the upper end of the. cone-shaped line 33, and is spaced therefrom to permit the ingress of upwardly passing air through the space provided between the two cones.

The several parts of the stack assembly including the outer shell 46, the Venturi cone 54 and cap 5 8 are supported as a unit from the back plate I4 by means of the two solid brackets 48 to which the outer shell 4% is bolted. As best shown in Fig. 2, a bolt 59 secures both the shell 46 and Venturi cone in position with relation to the upper bracket 48 and back plate M. Two additional bolts 56 are provided at spaced intervals about the shell 46 to secure the Venturi cone 54 in position with relation to the shell 48. The supporting straps 52 above referred to as supporting the cap 58 are secured at their lower ends to the Venturi cone 54.

A feature of the invention consists in the use of the- Venturi exit cone 5 and the baffle entrance cone 38 associated therewith to provide for a more rapid and eificient circulation of air by a heater shaped and arranged to occupy a minimum amount of usable space within the en- Where V1=fiuidvelocity at the upstream orifice connection in .ft. per sec.

G=acceleration of gravity in ft. per sec. per sec.

P1=static pressure at the upstream connection in pounds per sq. ft.

'P=fiuid density in pounds per cubic it.

V2=fluid velocity at the downstream orifice connection in ft. per sec.

Pz=static pressure at the downstream connection in pounds per sq. ft.

The Venturi cone 54 provided in accordance with the present invention, has been found well adapted to obtain a maximum dififerential between the value of the static pressure P: at the lower end or throat oi the Venturi cone 5; and the value of the static pressure P1 at the upper end of the Venturi cone '54 with a minimum of permanent loss.

For efficient operation of the heater, and more particularly to maintain the desired balance of pressures and velocities at the two ends of the Venturi cone 54, it is preferred to introduce the heated gases at the throat of the Venturi discharge cone 54 at a high velocity. Another feature of the invention consists in the provision of the entrance bafiie or plenum cone 38 which acts to provide a maximum increase of velocity at the throat of the Venturi cone 54 without at the same time creating excessive turbulence of the air currents at this point. The gases passing through the discharge Venturi cone 54 will now be brought to their initial velocity smoothly and without permanent pressure loss. The relatively small area of the orifice provided by the bafiie cone 38 has the effect of substantially increasing the velocity which is obtained by converting static or pressure energy into kinetic or velocity energy. As the fluid flows through the orifice of the entrance cone 38, the velocity increases to form a jet having a smaller area than that of the orifice. The point of greatest contraction .is defined as the vena contracta, and has the lowest static pressure P2. In a closed conductor the vena contracta area tends to become a vacuum. In the illustrated construction, the throat of the exit Venturi cone 54 is open, causing room air to be inspired at an accelerated rate so that the hot gases are diluted, lowering the discharge temperature of the heater. The illustrated construction'hasthe advantage that it cause; a substan tially increased volume of air from the heated space to pass through the heater, and thus "'ncreases the number of air changes per hour, 2' h the result that a greater distribution and consequently more accurate temperature control are obtained.

The upper rim of the Venturi cone 54 is disposed slightly below the upper edge or rim of the cylindrical shell 46, and is spaced therefrom sumciently to permit the flow of a cooling current of air upwardly between the wall of the Venturi cone 54 and the wall of the cylindrical shell 46, so that the exterior surface of the heater is adequately cooled. In order to insure that the cap 50 through which the heated air is discharged from the heater does not become overheated, an air space designated at 56 is provided between the upper rim of the shell 46 and the bottom rim of the cap 50. With this construction, an additional quantity of cold air is adapted to be mixed with the hot air rising through the Venturi cone 54, with the result that the temperature of the air discharged through the orifice is still further reduced.

The arrangement of the cylindrical shell 46 in combination with the cone-shaped flue 3B and Venturi cone 54 provides for a most efficient control of the heat disseminated from the burner l8 to provide for the discharge of large quantities of hot air, while at the same time all external surfaces including the cylindrical base IS, the cylindrical shell 46 and the discharge orifice carrying member 50 are sufiiciently cooled by the rapid circulation of cold air within the heater to avoid any risk of overheating or damage to portions of the load which may come in contact therewith.

It will be understood that the invention is not limited to the specific embodiment shown, and that various deviations may be made therefrom without departing from the spirit and scope of the appended claims.

What is claimed is:

l. A heater unit which comprises a base, a burner mounted in the base, a cover enclosing said base having an entrance bafile cone with upwardly convergin sides and anorifice at upper end disposed over said burner, a Venturi exit cone having upwardly diverging sides and with the bottom rim thereof overlapping and spaced from said upper end of the entrance bafiie cone, a tubular shell disposed above and separated from said base and enclosing and separated from said cones, providing a cold air inlet passage inside the shell from the bottom thereof into the Venturi cone and from the bottom to the top of the shell between the shell and said cones, and a tubular cap supported above and separated from said shell and cones, providing at its lower end a passage connecting with said Venturi cone and a cold air inlet passage between the shell and the cone and having a discharge orifice at its upper end.

2. A heater having in combination, a base, a

vertically disposed Venturi conduit having at the lower end thereof a throat and upwardly diverging sides, a baflle entrance conduit having upwardly converging sides having an open top providing an orifice extending within and of smaller diameter than the throat of the Venturi conduit, a burner disposed beneath said baffle conduit, and a shell enclosing and separated from said conduits having the lower edge thereof extending below the throat of the Venturi conduit, to provide a cold air inlet passage inside the shell from the bottom thereof into the Venturi conduit and from the bottom to the top of the shell between the shell and said conduits.

3. A heater having in combination, a base, a gas-fired burner within the base, a cover enclosing said base having a ballie entrance conduit with upwardly converging sides terminating in an orifice disposed over said burner, a Venturi exit conduit disposed above the bafile entrance conduit having at the lower end thereof a throat of larger diameter than said orifice disposed to receive the stream of heated gases from the orifice of the baffle cone and separated therefrom to permit the ingress of additional air through said throat, and a shell enclosing and separated from said conduits providing a cool air inlet passage inside the shell from the bottom thereof to said throat and from the bottom to the top of the shell between the shell and said conduits.

4. A heater, having in combination, a support comprising a base plate and a vertically disposed back plate, a base, a burner within the base, a cover enclosing said base having a bafiie entrance cone with upwardly converging sides terminating in an orifice disposed over said burner, a Venturi exit cone with upwardly diverging sides having at its lower end a throat of larger diameter than and enclosing said orifice disposed to receive the stream of heated gases from said orifice and separated from said orifice to permit the ingress of additional air through said throat, a shell enclosing and separated from said cones providing a cool air inlet passage inside the shell from the bottom thereof to said throat and from the bottom to the top of the shell between the shell and said cones, a cap disposed above and separated from said shell and Venturi cone providing at its lower end a passage connecting with said Venturi cone and with a cold air inlet passage between the shell and the cone and providing at its upper end a discharge orifice, means supporting said shell from the back plate, means supporting the cap from the Venturi cone, and means supporting the Venturi cone from the shell.

5. A heater having, in combination, a base, a burner within the base, a cover enclosing said base having a baffle entrance conduit with upwardly converging sides terminating in an orifice disposed over said burner, a Venturi exit conduit disposed above the baflle entrance conduit having at the lower end thereof a throat of larger diameter than and enclosing said orifice disposed to receive the stream of heated gases from the orifice of the baffle conduit and separated therefrom to permit the ingress of additional air through said throat, a shell enclosing and spaced from said conduits having the lower edge thereof extending below the throat of the Venturi conduit providing a cool air inlet passage inside the shell from the bottom thereof to said throat and from the bottom to th top of the shell between the shell and said conduits, and a tubular cap disposed over and spaced from the shell and cones and having at its upper end a discharge orifice, and a screening element covering said discharge orifice.

HARRY W. JANSON. COLEMAN D. RODGERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,237,858 Ballenger Aug. 21, 1917 2,357,575 Benz Sept. 5, 1944 FOREIGN PATENTS Number Country Date 133,505 Great Britain Oct. 16, 1919 347,855 France Jan, 20, 1905 

